src/eric7/PdfViewer/PdfViewerWindow.py

# -*- coding: utf-8 -*-

# Copyright (c) 2023 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing the PDF viewer main window.
"""

import contextlib
import os
import pathlib

from PyQt6.QtCore import Qt, pyqtSignal, QSize, pyqtSlot, QPointF
from PyQt6.QtGui import QAction, QKeySequence, QGuiApplication, QActionGroup
from PyQt6.QtPdf import QPdfDocument
from PyQt6.QtPdfWidgets import QPdfView
from PyQt6.QtWidgets import (
    QWhatsThis, QMenu, QTabWidget, QSplitter, QToolBar, QDialog
)

from eric7 import Preferences
from eric7.EricGui import EricPixmapCache
from eric7.EricGui.EricAction import EricAction
from eric7.EricWidgets import EricFileDialog, EricMessageBox
from eric7.EricWidgets.EricMainWindow import EricMainWindow
from eric7.EricWidgets.EricStretchableSpacer import EricStretchableSpacer
from eric7.Globals import recentNamePdfFiles
from eric7.SystemUtilities import FileSystemUtilities

from .PdfPageSelector import PdfPageSelector
from .PdfZoomSelector import PdfZoomSelector


class PdfViewerWindow(EricMainWindow):
    """
    Class implementing the PDF viewer main window.

    @signal viewerClosed() emitted after the window was requested to close
    """

    viewerClosed = pyqtSignal()

    windows = []

    maxMenuFilePathLen = 75

    def __init__(self, fileName="", parent=None, fromEric=False, project=None):
        """
        Constructor

        @param fileName name of a file to load on startup
        @type str
        @param parent parent widget of this window
        @type QWidget
        @param fromEric flag indicating whether it was called from within
            eric
        @type bool
        @param project reference to the project object
        @type Project
        """
        super().__init__(parent)
        self.setObjectName("eric7_pdf_viewer")

        self.__fromEric = fromEric
        self.setWindowIcon(EricPixmapCache.getIcon("ericPdf"))

        self.__screenResolution = (
            QGuiApplication.primaryScreen().logicalDotsPerInch() / 72.0
        )

        if not self.__fromEric:
            self.setStyle(Preferences.getUI("Style"), Preferences.getUI("StyleSheet"))

        self.__pdfDocument = QPdfDocument(self)

        self.__cw = QSplitter(Qt.Orientation.Horizontal, self)
        self.__info = QTabWidget(self)
        self.__cw.addWidget(self.__info)
        self.__view = QPdfView(self)
        self.__view.setDocument(self.__pdfDocument)
        self.__cw.addWidget(self.__view)
        self.setCentralWidget(self.__cw)

        # create a few widgets needed in the toolbars
        self.__pageSelector = PdfPageSelector(self)
        self.__pageSelector.setDocument(self.__pdfDocument)
        self.__view.pageNavigator().currentPageChanged.connect(
            self.__pageSelector.setValue
        )
        self.__pageSelector.valueChanged.connect(self.__pageSelected)
        self.__pageSelector.gotoPage.connect(self.__gotoPage)

        self.__zoomSelector = PdfZoomSelector(self)
        self.__zoomSelector.reset()

        g = Preferences.getGeometry("PdfViewerGeometry")
        if g.isEmpty():
            s = QSize(1000, 1000)
            self.resize(s)
            self.__cw.setSizes([300, 700])
        else:
            self.restoreGeometry(g)

        self.__initActions()
        self.__initMenus()
        self.__initToolbars()
        self.__createStatusBar()

        self.__setDisplayMode()  # needs to be done after actions have been created

        self.__view.pageNavigator().backAvailableChanged.connect(
            self.backwardAct.setEnabled
        )
        self.__view.pageNavigator().forwardAvailableChanged.connect(
            self.forwardAct.setEnabled
        )

        self.__zoomSelector.zoomModeChanged.connect(self.__view.setZoomMode)
        self.__zoomSelector.zoomModeChanged.connect(self.__zoomModeChanged)
        self.__zoomSelector.zoomFactorChanged.connect(self.__view.setZoomFactor)
        self.__view.zoomFactorChanged.connect(self.__zoomSelector.setZoomFactor)
        self.__view.zoomModeChanged.connect(self.__zoomSelector.setZoomMode)

        PdfViewerWindow.windows.append(self)

        self.__restoreViewerState()

        self.__checkActions()

        self.__project = project
        self.__lastOpenPath = ""

        self.__recent = []
        self.__loadRecent()

        self.__setCurrentFile("")
        self.__setViewerTitle("")
        if fileName:
            self.__loadPdfFile(fileName)

    def __initActions(self):
        """
        Private method to define the user interface actions.
        """
        # list of all actions
        self.__actions = []

        self.__initFileActions()
        self.__initGotoActions()
        self.__initViewActions()
        self.__initHelpActions()

    def __initFileActions(self):
        """
        Private method to define the file related user interface actions.
        """
        self.newWindowAct = EricAction(
            self.tr("New Window"),
            EricPixmapCache.getIcon("newWindow"),
            self.tr("New &Window"),
            QKeySequence(self.tr("Ctrl+Shift+N", "File|New Window")),
            0,
            self,
            "pdfviewer_file_new_window",
        )
        self.newWindowAct.setStatusTip(
            self.tr("Open a PDF file in a new PDF Viewer window")
        )
        self.newWindowAct.setWhatsThis(
            self.tr(
                """<b>New Window</b>"""
                """<p>This opens a PDF file in a new PDF Viewer window. It pops up"""
                """ a file selection dialog.</p>"""
            )
        )
        self.newWindowAct.triggered.connect(self.__openPdfFileNewWindow)
        self.__actions.append(self.newWindowAct)

        self.openAct = EricAction(
            self.tr("Open"),
            EricPixmapCache.getIcon("open"),
            self.tr("&Open..."),
            QKeySequence(self.tr("Ctrl+O", "File|Open")),
            0,
            self,
            "pdfviewer_file_open",
        )
        self.openAct.setStatusTip(self.tr("Open a PDF file for viewing"))
        self.openAct.setWhatsThis(
            self.tr(
                """<b>Open</b>"""
                """<p>This opens a PDF file for viewing. It pops up a file"""
                """ selection dialog.</p>"""
            )
        )
        self.openAct.triggered.connect(self.__openPdfFile)
        self.__actions.append(self.openAct)

        self.reloadAct = EricAction(
            self.tr("Reload"),
            EricPixmapCache.getIcon("reload"),
            self.tr("&Reload"),
            QKeySequence("F5"),
            0,
            self,
            "pdfviewer_file_reload",
        )
        self.reloadAct.setStatusTip(self.tr("Reload the current PDF document"))
        self.reloadAct.triggered.connect(self.__reload)
        self.__actions.append(self.reloadAct)

        # TODO: maybe this will be a tab of the side widget
        self.propertiesAct = EricAction(
            self.tr("Properties"),
            EricPixmapCache.getIcon("documentProperties"),
            self.tr("&Properties..."),
            QKeySequence(self.tr("Alt+Return")),
            0,
            self,
            "pdfviewer_file_properties",
        )
        self.propertiesAct.setStatusTip(self.tr("Show the document properties"))
        self.propertiesAct.setWhatsThis(
            self.tr(
                """<b>Properties</b><p>Opens a dialog showing the document"""
                """ properties.</p>"""
            )
        )
        self.propertiesAct.triggered.connect(self.__showDocumentProperties)
        self.__actions.append(self.propertiesAct)

        self.closeAct = EricAction(
            self.tr("Close"),
            EricPixmapCache.getIcon("close"),
            self.tr("&Close"),
            QKeySequence(self.tr("Ctrl+W", "File|Close")),
            0,
            self,
            "pdfviewer_file_close",
        )
        self.closeAct.setStatusTip(self.tr("Close the current PDF Viewer window"))
        self.closeAct.triggered.connect(self.close)
        self.__actions.append(self.closeAct)

        self.closeAllAct = EricAction(
            self.tr("Close All"),
            self.tr("Close &All"),
            0,
            0,
            self,
            "pdfviewer_file_close_all",
        )
        self.closeAllAct.setStatusTip(self.tr("Close all PDF Viewer windows"))
        self.closeAllAct.triggered.connect(self.__closeAll)
        self.__actions.append(self.closeAllAct)

        self.closeOthersAct = EricAction(
            self.tr("Close Others"),
            self.tr("Close Others"),
            0,
            0,
            self,
            "pdfviewer_file_close_others",
        )
        self.closeOthersAct.setStatusTip(self.tr("Close all other PDF Viewer windows"))
        self.closeOthersAct.triggered.connect(self.__closeOthers)
        self.__actions.append(self.closeOthersAct)

        self.exitAct = EricAction(
            self.tr("Quit"),
            EricPixmapCache.getIcon("exit"),
            self.tr("&Quit"),
            QKeySequence(self.tr("Ctrl+Q", "File|Quit")),
            0,
            self,
            "pdfviewer_file_quit",
        )
        self.exitAct.setStatusTip(self.tr("Quit the PDF Viewer"))
        if not self.__fromEric:
            self.exitAct.triggered.connect(self.__closeAll)
        self.__actions.append(self.exitAct)

    def __initGotoActions(self):
        """
        Private method to define the navigation related user interface actions.
        """
        self.previousPageAct = EricAction(
            self.tr("Previous Page"),
            EricPixmapCache.getIcon("1leftarrow"),
            self.tr("&Previous Page"),
            0,
            0,
            self,
            "pdfviewer_goto_previous",
        )
        self.previousPageAct.setStatusTip(self.tr("Go to the previous page"))
        self.previousPageAct.triggered.connect(self.__previousPage)
        self.__actions.append(self.previousPageAct)

        self.nextPageAct = EricAction(
            self.tr("Next Page"),
            EricPixmapCache.getIcon("1rightarrow"),
            self.tr("&Next Page"),
            0,
            0,
            self,
            "pdfviewer_goto_next",
        )
        self.nextPageAct.setStatusTip(self.tr("Go to the next page"))
        self.nextPageAct.triggered.connect(self.__nextPage)
        self.__actions.append(self.nextPageAct)

        self.startDocumentAct = EricAction(
            self.tr("Start of Document"),
            EricPixmapCache.getIcon("gotoFirst"),
            self.tr("&Start of Document"),
            QKeySequence(self.tr("Ctrl+Home", "Goto|Start")),
            0,
            self,
            "pdfviewer_goto_start",
        )
        self.startDocumentAct.setStatusTip(
            self.tr("Go to the first page of the document")
        )
        self.startDocumentAct.triggered.connect(self.__startDocument)
        self.__actions.append(self.startDocumentAct)

        self.endDocumentAct = EricAction(
            self.tr("End of Document"),
            EricPixmapCache.getIcon("gotoLast"),
            self.tr("&End of Document"),
            QKeySequence(self.tr("Ctrl+End", "Goto|End")),
            0,
            self,
            "pdfviewer_goto_end",
        )
        self.endDocumentAct.setStatusTip(
            self.tr("Go to the last page of the document")
        )
        self.endDocumentAct.triggered.connect(self.__endDocument)
        self.__actions.append(self.endDocumentAct)

        self.backwardAct = EricAction(
            self.tr("Back"),
            EricPixmapCache.getIcon("back"),
            self.tr("&Back"),
            QKeySequence(self.tr("Alt+Shift+Left", "Goto|Back")),
            0,
            self,
            "pdfviewer_goto_back",
        )
        self.backwardAct.setStatusTip(
            self.tr("Go back in the view history")
        )
        self.backwardAct.triggered.connect(self.__backInHistory)
        self.__actions.append(self.backwardAct)

        self.forwardAct = EricAction(
            self.tr("Forward"),
            EricPixmapCache.getIcon("forward"),
            self.tr("&Forward"),
            QKeySequence(self.tr("Alt+Shift+Right", "Goto|Forward")),
            0,
            self,
            "pdfviewer_goto_forward",
        )
        self.forwardAct.setStatusTip(
            self.tr("Go forward in the view history")
        )
        self.forwardAct.triggered.connect(self.__forwardInHistory)
        self.__actions.append(self.forwardAct)

        self.gotoAct = EricAction(
            self.tr("Go to Page"),
            EricPixmapCache.getIcon("gotoJump"),
            self.tr("&Go to Page..."),
            QKeySequence(self.tr("Ctrl+G", "Goto|Go to Page")),
            0,
            self,
            "pdfviewer_goto_gotopage",
        )
        self.gotoAct.setStatusTip(
            self.tr("Jump to a page selected via a dialog")
        )
        self.gotoAct.triggered.connect(self.__gotoPage)
        self.__actions.append(self.gotoAct)

    def __initViewActions(self):
        """
        Private method to define the view related user interface actions.
        """
        self.zoomInAct = EricAction(
            self.tr("Zoom in"),
            EricPixmapCache.getIcon("zoomIn"),
            self.tr("Zoom &in"),
            QKeySequence(self.tr("Ctrl++", "View|Zoom in")),
            0,
            self,
            "pdfviewer_view_zoomin",
        )
        self.zoomInAct.triggered.connect(self.__zoomIn)
        self.__actions.append(self.zoomInAct)

        self.zoomOutAct = EricAction(
            self.tr("Zoom out"),
            EricPixmapCache.getIcon("zoomOut"),
            self.tr("Zoom &out"),
            QKeySequence(self.tr("Ctrl+-", "View|Zoom out")),
            0,
            self,
            "pdfviewer_view_zoomout",
        )
        self.zoomOutAct.triggered.connect(self.__zoomOut)
        self.__actions.append(self.zoomOutAct)

        self.zoomResetAct = EricAction(
            self.tr("Zoom to 100%"),
            EricPixmapCache.getIcon("zoomReset"),
            self.tr("Zoom to &100%"),
            QKeySequence(self.tr("Ctrl+0", "View|Zoom reset")),
            0,
            self,
            "pdfviewer_view_zoomreset",
        )
        self.zoomResetAct.triggered.connect(self.__zoomReset)
        self.__actions.append(self.zoomResetAct)

        self.zoomPageWidthAct = EricAction(
            self.tr("Page Width"),
            EricPixmapCache.getIcon("zoomFitWidth"),
            self.tr("Page &Width"),
            0,
            0,
            self,
            "pdfviewer_view_zoompagewidth",
        )
        self.zoomPageWidthAct.triggered.connect(self.__zoomPageWidth)
        self.zoomPageWidthAct.setCheckable(True)
        self.__actions.append(self.zoomPageWidthAct)

        self.zoomWholePageAct = EricAction(
            self.tr("Whole Page"),
            EricPixmapCache.getIcon("zoomFitPage"),
            self.tr("Whole &Page"),
            0,
            0,
            self,
            "pdfviewer_view_zoomwholePage",
        )
        self.zoomWholePageAct.triggered.connect(self.__zoomWholePage)
        self.zoomWholePageAct.setCheckable(True)
        self.__actions.append(self.zoomWholePageAct)

        ##self.__displayModeActGrp = QActionGroup(self)
##
        ##self.displayModeSingleAct = EricAction(
            ##self.tr("Whole Page"),
            ##EricPixmapCache.getIcon("zoomFitPage"),
            ##self.tr("Whole &Page"),
            ##0,
            ##0,
            ##self,
            ##"pdfviewer_view_zoomwholePage",
        ##)
        ##self.displayModeSingleAct.triggered.connect(self.__zoomWholePage)
        ##self.displayModeSingleAct.setCheckable(True)
        ##self.__actions.append(self.displayModeSingleAct)

    def __initHelpActions(self):
        """
        Private method to create the Help actions.
        """
        self.aboutAct = EricAction(
            self.tr("About"), self.tr("&About"), 0, 0, self, "pdfviewer_help_about"
        )
        self.aboutAct.setStatusTip(self.tr("Display information about this software"))
        self.aboutAct.setWhatsThis(
            self.tr(
                """<b>About</b>"""
                """<p>Display some information about this software.</p>"""
            )
        )
        self.aboutAct.triggered.connect(self.__about)
        self.__actions.append(self.aboutAct)

        self.aboutQtAct = EricAction(
            self.tr("About Qt"),
            self.tr("About &Qt"),
            0,
            0,
            self,
            "pdfviewer_help_about_qt",
        )
        self.aboutQtAct.setStatusTip(
            self.tr("Display information about the Qt toolkit")
        )
        self.aboutQtAct.setWhatsThis(
            self.tr(
                """<b>About Qt</b>"""
                """<p>Display some information about the Qt toolkit.</p>"""
            )
        )
        self.aboutQtAct.triggered.connect(self.__aboutQt)
        self.__actions.append(self.aboutQtAct)

        self.whatsThisAct = EricAction(
            self.tr("What's This?"),
            EricPixmapCache.getIcon("whatsThis"),
            self.tr("&What's This?"),
            QKeySequence(self.tr("Shift+F1", "Help|What's This?'")),
            0,
            self,
            "pdfviewer_help_whats_this",
        )
        self.whatsThisAct.setStatusTip(self.tr("Context sensitive help"))
        self.whatsThisAct.setWhatsThis(
            self.tr(
                """<b>Display context sensitive help</b>"""
                """<p>In What's This? mode, the mouse cursor shows an arrow"""
                """ with a question mark, and you can click on the interface"""
                """ elements to get a short description of what they do and"""
                """ how to use them. In dialogs, this feature can be accessed"""
                """ using the context help button in the titlebar.</p>"""
            )
        )
        self.whatsThisAct.triggered.connect(self.__whatsThis)
        self.__actions.append(self.whatsThisAct)

    @pyqtSlot()
    def __checkActions(self):
        """
        Private slot to check some actions for their enable/disable status.
        """
        ready = self.__pdfDocument.status() == QPdfDocument.Status.Ready

        self.reloadAct.setEnabled(ready)
        self.propertiesAct.setEnabled(ready)

        curPage = self.__view.pageNavigator().currentPage()
        self.previousPageAct.setEnabled(curPage > 0 and ready)
        self.nextPageAct.setEnabled(
            curPage < self.__pdfDocument.pageCount() - 1 and ready
        )
        self.startDocumentAct.setEnabled(curPage != 0 and ready)
        self.endDocumentAct.setEnabled(
            curPage != self.__pdfDocument.pageCount() - 1 and ready
        )
        self.gotoAct.setEnabled(ready)

        self.backwardAct.setEnabled(self.__view.pageNavigator().backAvailable())
        self.forwardAct.setEnabled(self.__view.pageNavigator().forwardAvailable())

        self.zoomInAct.setEnabled(ready)
        self.zoomOutAct.setEnabled(ready)
        self.zoomResetAct.setEnabled(ready)
        self.zoomPageWidthAct.setEnabled(ready)
        self.zoomWholePageAct.setEnabled(ready)
        self.__zoomSelector.setEnabled(ready)

        # TODO: not yet implemented

    ##def setRecentPath(self, openPath):
        ##"""
        ##Public method to set the last open path.
##
        ##@param openPath least recently used open path
        ##@type str
        ##"""
        ##if openPath:
            ##self.__lastOpenPath = openPath

    def __initMenus(self):
        """
        Private method to create the menus.
        """
        mb = self.menuBar()

        menu = mb.addMenu(self.tr("&File"))
        menu.setTearOffEnabled(True)
        self.__recentMenu = QMenu(self.tr("Open &Recent Files"), menu)
        menu.addAction(self.newWindowAct)
        menu.addAction(self.openAct)
        self.__menuRecentAct = menu.addMenu(self.__recentMenu)
        menu.addSeparator()
        menu.addAction(self.reloadAct)
        menu.addSeparator()
        menu.addAction(self.propertiesAct)
        menu.addSeparator()
        menu.addAction(self.closeAct)
        menu.addAction(self.closeOthersAct)
        if self.__fromEric:
            menu.addAction(self.closeAllAct)
        else:
            menu.addSeparator()
            menu.addAction(self.exitAct)
        menu.aboutToShow.connect(self.__showFileMenu)
        self.__recentMenu.aboutToShow.connect(self.__showRecentMenu)
        self.__recentMenu.triggered.connect(self.__openRecentPdfFile)

        menu = mb.addMenu(self.tr("&View"))
        menu.setTearOffEnabled(True)
        menu.addAction(self.zoomInAct)
        menu.addAction(self.zoomOutAct)
        menu.addAction(self.zoomResetAct)
        menu.addAction(self.zoomPageWidthAct)
        menu.addAction(self.zoomWholePageAct)
        menu.addSeparator()
        modeMenu = menu.addMenu(self.tr("Display Mode"))
        self.__singlePageAct = modeMenu.addAction(self.tr("Single Page"))
        self.__singlePageAct.setCheckable(True)
        self.__continuousPageAct = modeMenu.addAction(self.tr("Continuous"))
        self.__continuousPageAct.setCheckable(True)
        self.__displayModeActGrp = QActionGroup(self)
        self.__displayModeActGrp.addAction(self.__singlePageAct)
        self.__displayModeActGrp.addAction(self.__continuousPageAct)
        modeMenu.triggered.connect(self.__displayModeSelected)

        menu = mb.addMenu(self.tr("&Go To"))
        menu.setTearOffEnabled(True)
        menu.addAction(self.previousPageAct)
        menu.addAction(self.nextPageAct)
        menu.addSeparator()
        menu.addAction(self.startDocumentAct)
        menu.addAction(self.endDocumentAct)
        menu.addSeparator()
        menu.addAction(self.backwardAct)
        menu.addAction(self.forwardAct)
        menu.addSeparator()
        menu.addAction(self.gotoAct)

        mb.addSeparator()

        menu = mb.addMenu(self.tr("&Help"))
        menu.addAction(self.aboutAct)
        menu.addAction(self.aboutQtAct)
        menu.addSeparator()
        menu.addAction(self.whatsThisAct)

    def __initToolbars(self):
        """
        Private method to create the toolbars.
        """
        mainToolBar = QToolBar()
        mainToolBar.setObjectName("main_toolbar")
        mainToolBar.setMovable(False)
        mainToolBar.setFloatable(False)

        # 1. File actions
        mainToolBar.addAction(self.newWindowAct)
        mainToolBar.addAction(self.openAct)
        mainToolBar.addSeparator()
        mainToolBar.addAction(self.closeAct)
        if not self.__fromEric:
            mainToolBar.addAction(self.exitAct)
        mainToolBar.addSeparator()

        # 2. Go to actions
        mainToolBar.addWidget(EricStretchableSpacer())
        mainToolBar.addAction(self.startDocumentAct)
        mainToolBar.addWidget(self.__pageSelector)
        mainToolBar.addAction(self.endDocumentAct)
        mainToolBar.addWidget(EricStretchableSpacer())
        mainToolBar.addSeparator()

        # 3. View actions
        # TODO: not yet implemented
        mainToolBar.addAction(self.zoomOutAct)
        mainToolBar.addWidget(self.__zoomSelector)
        mainToolBar.addAction(self.zoomInAct)
        mainToolBar.addAction(self.zoomResetAct)
        mainToolBar.addAction(self.zoomPageWidthAct)
        mainToolBar.addAction(self.zoomWholePageAct)

        self.addToolBar(mainToolBar)
        self.addToolBarBreak()

    def __createStatusBar(self):
        """
        Private method to initialize the status bar.
        """
        self.__statusBar = self.statusBar()
        self.__statusBar.setSizeGripEnabled(True)

        # not yet implemented

    def closeEvent(self, evt):
        """
        Protected method handling the close event.

        @param evt reference to the close event
        @type QCloseEvent
        """
        Preferences.setGeometry("PdfViewerGeometry", self.saveGeometry())

        self.__saveViewerState()

        with contextlib.suppress(ValueError):
            if self.__fromEric or len(PdfViewerWindow.windows) > 1:
                PdfViewerWindow.windows.remove(self)

        self.__saveRecent()

        evt.accept()
        self.viewerClosed.emit()

    def __saveViewerState(self):
        """
        Private method to save the PDF Viewer state data.
        """
        # TODO: save current zoom factor and mode + page mode
        state = self.saveState()
        Preferences.setPdfViewer("PdfViewerState", state)
        splitterState = self.__cw.saveState()
        Preferences.setPdfViewer("PdfViewerSplitterState", splitterState)

        if not self.__fromEric:
            Preferences.syncPreferences()

    def __restoreViewerState(self):
        """
        Private method to restore the PDF Viewer state data.
        """
        # TODO: restore zoom factor and mode + page mode
        state = Preferences.getPdfViewer("PdfViewerState")
        self.restoreState(state)
        splitterState = Preferences.getPdfViewer("PdfViewerSplitterState")
        self.__cw.restoreState(splitterState)

    def __setViewerTitle(self, title):
        """
        Private method to set the viewer title.

        @param title title to be set
        @type str
        """
        if title:
            self.setWindowTitle(self.tr("{0} - PDF Viewer").format(title))
        else:
            self.setWindowTitle(self.tr("PDF Viewer"))

    def __getErrorString(self, err):
        """
        Private method to get an error string for the given error.

        @param err error type
        @type QPdfDocument.Error
        @return string for the given error type
        @rtype str
        """
        if err == QPdfDocument.Error.None_:
            reason = ""
        elif err == QPdfDocument.Error.DataNotYetAvailable:
            reason = self.tr("The document is still loading.")
        elif err == QPdfDocument.Error.FileNotFound:
            reason = self.tr("The file does not exist.")
        elif err == QPdfDocument.Error.InvalidFileFormat:
            reason = self.tr("The file is not a valid PDF file.")
        elif err == QPdfDocument.Error.IncorrectPassword:
            reason = self.tr("The password is not correct for this file.")
        elif err == QPdfDocument.Error.UnsupportedSecurityScheme:
            reason = self.tr("This kind of PDF file cannot be unlocked.")
        else:
            reason = self.tr("Unknown type of error.")

        return reason

    def __loadPdfFile(self, fileName):
        """
        Private method to load a PDF file.

        @param fileName path of the PDF file to load
        @type str
        """
        # TODO: if error is QPdfDocument.Error.IncorrectPassword ask for PW and try
        #       again until cancelled
        err = self.__pdfDocument.load(fileName)
        if err != QPdfDocument.Error.None_:
            EricMessageBox.critical(
                self,
                self.tr("Load PDF File"),
                self.tr(
                    """<p>The PDF file <b>{0}</b> could not be loaded.</p>"""
                    """<p>Reason: {1}</p>"""
                ).format(fileName, self.__getErrorString(err)),
            )
            return

        self.__lastOpenPath = os.path.dirname(fileName)
        self.__setCurrentFile(fileName)

        documentTitle = self.__pdfDocument.metaData(QPdfDocument.MetaDataField.Title)
        self.__setViewerTitle(documentTitle)

        self.__pageSelected(0)
        self.__pageSelector.setMaximum(self.__pdfDocument.pageCount() - 1)
        self.__pageSelector.setValue(0)

    @pyqtSlot()
    def __reload(self):
        """
        Private slot to reload the current PDF document.
        """
        self.__loadPdfFile(self.__fileName)

    @pyqtSlot()
    def __openPdfFile(self):
        """
        Private slot to open a PDF file.
        """
        if (
            not self.__lastOpenPath
            and self.__project is not None
            and self.__project.isOpen()
        ):
            self.__lastOpenPath = self.__project.getProjectPath()

        fileName = EricFileDialog.getOpenFileName(
            self,
            self.tr("Open PDF File"),
            self.__lastOpenPath,
            self.tr("PDF Files (*.pdf);;All Files (*)"),
        )
        if fileName:
            self.__loadPdfFile(fileName)

    @pyqtSlot()
    def __openPdfFileNewWindow(self):
        """
        Private slot called to open a PDF file in new viewer window.
        """
        if (
            not self.__lastOpenPath
            and self.__project is not None
            and self.__project.isOpen()
        ):
            self.__lastOpenPath = self.__project.getProjectPath()

        fileName = EricFileDialog.getOpenFileName(
            self,
            self.tr("Open PDF File"),
            self.__lastOpenPath,
            self.tr("PDF Files (*.pdf);;All Files (*)"),
        )
        if fileName:
            viewer = PdfViewerWindow(
                fileName=fileName,
                parent=self.parent(),
                fromEric=self.__fromEric,
                project=self.__project,
            )
            viewer.show()

    @pyqtSlot()
    def __closeAll(self):
        """
        Private slot to close all windows.
        """
        self.__closeOthers()
        self.close()

    @pyqtSlot()
    def __closeOthers(self):
        """
        Private slot to close all other windows.
        """
        for win in PdfViewerWindow.windows[:]:
            if win != self:
                win.close()

    @pyqtSlot(int)
    def __pageSelected(self, page):
        """
        Private slot to navigate to the given page.

        @param page index of the page to be shown
        @type int
        """
        nav = self.__view.pageNavigator()
        nav.jump(page, QPointF(), nav.currentZoom())

        self.__checkActions()

    def __setCurrentFile(self, fileName):
        """
        Private method to register the file name of the current file.

        @param fileName name of the file to register
        @type str
        """
        self.__fileName = fileName
        # insert filename into list of recently opened files
        self.__addToRecentList(fileName)

    @pyqtSlot()
    def __about(self):
        """
        Private slot to show a little About message.
        """
        EricMessageBox.about(
            self,
            self.tr("About eric PDF Viewer"),
            self.tr(
                "The eric PDF Viewer is a simple component for viewing PDF files."
            ),
        )

    @pyqtSlot()
    def __aboutQt(self):
        """
        Private slot to handle the About Qt dialog.
        """
        EricMessageBox.aboutQt(self, "eric PDF Viewer")

    @pyqtSlot()
    def __whatsThis(self):
        """
        Private slot called in to enter Whats This mode.
        """
        QWhatsThis.enterWhatsThisMode()

    @pyqtSlot()
    def __showPreferences(self):
        """
        Private slot to set the preferences.
        """
        from eric7.Preferences.ConfigurationDialog import (
            ConfigurationDialog,
            ConfigurationMode,
        )

        # TODO: not yet implemented

    @pyqtSlot()
    def __showFileMenu(self):
        """
        Private slot to modify the file menu before being shown.
        """
        self.__menuRecentAct.setEnabled(len(self.__recent) > 0)

    @pyqtSlot()
    def __showRecentMenu(self):
        """
        Private slot to set up the recent files menu.
        """
        self.__loadRecent()

        self.__recentMenu.clear()

        for idx, rs in enumerate(self.__recent, start=1):
            formatStr = "&{0:d}. {1}" if idx < 10 else "{0:d}. {1}"
            act = self.__recentMenu.addAction(
                formatStr.format(
                    idx,
                    FileSystemUtilities.compactPath(
                        rs, PdfViewerWindow.maxMenuFilePathLen
                    ),
                )
            )
            act.setData(rs)
            act.setEnabled(pathlib.Path(rs).exists())

        self.__recentMenu.addSeparator()
        self.__recentMenu.addAction(self.tr("&Clear"), self.__clearRecent)

    @pyqtSlot(QAction)
    def __openRecentPdfFile(self, act):
        """
        Private method to open a file from the list of recently opened files.

        @param act reference to the action that triggered
        @type QAction
        """
        # TODO: add config option to open recent files in new viewer or the same one
        fileName = act.data()
        self.__loadPdfFile(fileName)

    @pyqtSlot()
    def __clearRecent(self):
        """
        Private method to clear the list of recently opened files.
        """
        self.__recent = []

    def __loadRecent(self):
        """
        Private method to load the list of recently opened files.
        """
        self.__recent = []
        Preferences.Prefs.rsettings.sync()
        rs = Preferences.Prefs.rsettings.value(recentNamePdfFiles)
        if rs is not None:
            for f in Preferences.toList(rs):
                if pathlib.Path(f).exists():
                    self.__recent.append(f)

    def __saveRecent(self):
        """
        Private method to save the list of recently opened files.
        """
        Preferences.Prefs.rsettings.setValue(recentNamePdfFiles, self.__recent)
        Preferences.Prefs.rsettings.sync()

    def __addToRecentList(self, fileName):
        """
        Private method to add a file name to the list of recently opened files.

        @param fileName name of the file to be added
        """
        if fileName:
            for recent in self.__recent[:]:
                if FileSystemUtilities.samepath(fileName, recent):
                    self.__recent.remove(recent)
            self.__recent.insert(0, fileName)
            maxRecent = Preferences.getPdfViewer("RecentNumber")
            if len(self.__recent) > maxRecent:
                self.__recent = self.__recent[:maxRecent]
            self.__saveRecent()

    @pyqtSlot()
    def __showDocumentProperties(self):
        """
        Private slot to open a dialog showing the document properties.
        """
        # TODO: not yet implemented

    @pyqtSlot()
    def __gotoPage(self):
        """
        Private slot to show a dialog to select a page to jump to.
        """
        # TODO: not yet implemented
        from .PdfGoToDialog import PdfGoToDialog

        dlg = PdfGoToDialog(
            self.__view.pageNavigator().currentPage(),
            self.__pdfDocument.pageCount(),
            self,
        )
        if dlg.exec() == QDialog.DialogCode.Accepted:
            page = dlg.getPage()
            self.__pageSelected(page)

    @pyqtSlot()
    def __previousPage(self):
        """
        Private slot to go to the previous page.
        """
        curPage = self.__view.pageNavigator().currentPage()
        if curPage > 0:
            self.__pageSelected(curPage - 1)

    @pyqtSlot()
    def __nextPage(self):
        """
        Private slot to go to the next page.
        """
        curPage = self.__view.pageNavigator().currentPage()
        if curPage < self.__pdfDocument.pageCount() - 1:
            self.__pageSelected(curPage + 1)

    @pyqtSlot()
    def __startDocument(self):
        """
        Private slot to go to the first page of the document.
        """
        self.__pageSelected(0)

    @pyqtSlot()
    def __endDocument(self):
        """
        Private slot to go to the last page of the document.
        """
        self.__pageSelected(self.__pdfDocument.pageCount() - 1)

    @pyqtSlot()
    def __backInHistory(self):
        """
        Private slot to go back in the view history.
        """
        self.__view.pageNavigator().back()

    @pyqtSlot()
    def __forwardInHistory(self):
        """
        Private slot to go forward in the view history.
        """
        self.__view.pageNavigator().forward()

    def __zoomInOut(self, zoomIn):
        """
        Private method to zoom into or out of the view.

        @param zoomIn flag indicating to zoom into the view
        @type bool
        """
        zoomFactor = self.__zoomFactorForMode(self.__view.zoomMode())

        factors = list(PdfZoomSelector.ZoomValues)
        factors.append(self.__zoomFactorForMode(QPdfView.ZoomMode.FitInView))
        factors.append(self.__zoomFactorForMode(QPdfView.ZoomMode.FitToWidth))
        if zoomIn:
            factors.sort()
            if zoomFactor >= factors[-1]:
                return
            newIndex = next(x for x, val in enumerate(factors) if val > zoomFactor)
        else:
            factors.sort(reverse=True)
            if zoomFactor <= factors[-1]:
                return
            newIndex = next(x for x, val in enumerate(factors) if val < zoomFactor)
        newFactor = factors[newIndex]
        if newFactor == self.__zoomFactorForMode(QPdfView.ZoomMode.FitInView):
            self.__zoomWholePage(True)
        elif newFactor == self.__zoomFactorForMode(QPdfView.ZoomMode.FitToWidth):
            self.__zoomPageWidth(True)
        else:
            self.__view.setZoomFactor(newFactor)
            self.__zoomSelector.setZoomFactor(newFactor)
            self.__zoomModeChanged(QPdfView.ZoomMode.Custom)

    @pyqtSlot()
    def __zoomIn(self):
        """
        Private slot to zoom into the view.
        """
        self.__zoomInOut(True)

    @pyqtSlot()
    def __zoomOut(self):
        """
        Private slot to zoom out of the view.
        """
        self.__zoomInOut(False)

    @pyqtSlot()
    def __zoomReset(self):
        """
        Private slot to reset the zoom factor of the view.
        """
        self.__view.setZoomFactor(1.0)
        self.__zoomSelector.setZoomFactor(1.0)
        self.__zoomModeChanged(QPdfView.ZoomMode.Custom)

    @pyqtSlot(bool)
    def __zoomPageWidth(self, checked):
        """
        Private slot to fit the page width.

        @param checked flag indicating the check state
        @type bool
        """
        if checked:
            self.__view.setZoomMode(QPdfView.ZoomMode.FitToWidth)
            self.zoomWholePageAct.setChecked(False)

    @pyqtSlot(bool)
    def __zoomWholePage(self, checked):
        """
        Private slot to fit the page width.

        @param checked flag indicating the check state
        @type bool
        """
        if checked:
            self.__view.setZoomMode(QPdfView.ZoomMode.FitInView)
            self.zoomPageWidthAct.setChecked(False)

    @pyqtSlot(QPdfView.ZoomMode)
    def __zoomModeChanged(self, zoomMode):
        """
        Private slot to handle a change of the zoom mode.

        @param zoomMode new zoom mode
        @type QPdfView.ZoomMode
        """
        self.zoomWholePageAct.setChecked(zoomMode == QPdfView.ZoomMode.FitInView)
        self.zoomPageWidthAct.setChecked(zoomMode == QPdfView.ZoomMode.FitToWidth)

    def __zoomFactorForMode(self, zoomMode):
        """
        Private method to calculate the zoom factor iaw. the current zoom mode.

        @param zoomMode zoom mode to get the zoom factor for
        @type QPdfView.ZoomMode
        @return zoom factor
        @rtype float
        """
        if zoomMode == QPdfView.ZoomMode.Custom:
            return self.__view.zoomFactor()
        else:
            viewport = self.__view.viewport()
            curPage = self.__view.pageNavigator().currentPage()
            margins = self.__view.documentMargins()
            if zoomMode == QPdfView.ZoomMode.FitToWidth:
                pageSize = (
                    self.__pdfDocument.pagePointSize(curPage) * self.__screenResolution
                ).toSize()
                factor = (
                    viewport.width() - margins.left() - margins.right()
                ) / pageSize.width()
                pageSize *= factor
            else:
                # QPdfView.ZoomMode.FitInView
                viewportSize = viewport.size() + QSize(
                    -margins.left() - margins.right(), -self.__view.pageSpacing()
                )
                pageSize = (
                    self.__pdfDocument.pagePointSize(curPage) * self.__screenResolution
                ).toSize()
                pageSize = pageSize.scaled(
                    viewportSize, Qt.AspectRatioMode.KeepAspectRatio
                )
            zoomFactor = pageSize.width() / (
                self.__pdfDocument.pagePointSize(curPage) * self.__screenResolution
            ).width()
            return zoomFactor

    @pyqtSlot()
    def __setFocusToView(self):
        """
        Private slot to set the focus to the PDF document view.
        """
        self.__view.setFocus(Qt.FocusReason.OtherFocusReason)

    @pyqtSlot(QAction)
    def __displayModeSelected(self, act):
        """
        Private slot to handle the selection of a display mode.

        @param act reference to the triggering action
        @type QAction
        """
        if act is self.__singlePageAct:
            Preferences.setPdfViewer("PdfViewerDisplayMode", "single")
        else:
            Preferences.setPdfViewer("PdfViewerDisplayMode", "continuous")
        self.__setDisplayMode()

    def __setDisplayMode(self):
        """
        Private method to set the display mode iaw. configuration.
        """
        if Preferences.getPdfViewer("PdfViewerDisplayMode") == "single":
            self.__view.setPageMode(QPdfView.PageMode.SinglePage)
            self.__singlePageAct.setChecked(True)
        else:
            self.__view.setPageMode(QPdfView.PageMode.MultiPage)
            self.__continuousPageAct.setChecked(True)
        return